An antenna transmits/receives an electromagnetic wave by radiating a radiation pattern, and has usually structure shown in below FIG. 1.
FIG. 1 is a perspective view illustrating a common antenna.
In FIG. 1, the antenna includes a reflection plate 100 and radiation devices 102.
The reflection plate 100 has a shape bent in a specific direction as shown in FIG. 1, and includes a base member 100A and a bending member 100B.
The radiation devices 102 are disposed in sequence on the reflection plate 100.
The antenna outputs a beam in a given direction using radiation patterns radiated from the radiation devices 102.
A phase shifter (not shown) is formed on a second surface opposed to a first surface of the reflection plate 100, wherein the radiation devices 102 are disposed on the first surface. This phase shifter changes phase of an inputted signal, and transmits the changed signal to the radiation devices 102, thereby adjusting direction of the beam.
On the other hand, the beam has constant characteristics without being changed, and so a choke member (not shown) is formed on the reflection plate 100 so as to change characteristics of the beam. In this case, the choke member made up of metal is directly formed on the reflection plate 100, and so passive intermodulation distortion (hereinafter, referred to as “PIMD”) is seriously occurred in the antenna.